I usually do a dot in the center and then spread it around a bit. It honestly doesn't make a huge difference if done right, because the pressure between the heatsink and heatspreader should spread it out.
According to their website the middle pitcure is the correct way to apply AS5.
Thats how I did it on my quad and my temps are staying in the low to mid 30's.
I shove my finger in some plastic wrap and stretch it out, to spread the dot thin. I've never tried the heatsink spread method, or the line one, but I get ok temps. I dunno if it really matters as long as you don't stick too much or too little.